Fin stabilizers serve to dampen rolling movements of watercraft or ships. In principle there are two types of fin stabilizers. Fin stabilizers including stabilizer fins retractable into the hull, and fin stabilizers including non-retractable stabilizer fins. The present invention relates to the fin stabilizers including a retractable stabilizer fin. For this purpose the fin stabilizers have a receiving space or fin box that is introduced into the hull and open to the water side via an opening. The fin box is sealed with respect to the hull interior. During retracting and extending the stabilizer fin enters or exits through the opening in the fin box. The opening is slightly larger than the cross-section of the stabilizer fin. In operation water is pressed or sucked into the fin box and impinges with high speed on a rear side wall, viewed in the direction of travel of the ship, of the fin box. In addition, a relatively strong circulation flow forms inside the fin box. A large flow resistance is thereby induced, which significantly increases the fuel consumption of the ship. Furthermore the maximum buoyancy-force and downthrust-force and thus the stabilization performance of the fin stabilizer is impaired by the fin-box opening.
For this reason covers have been developed for at least partial covering or closing of the opening. In one cover a stiff metal plate as cover element is deflected in the edge region of the opening and is pivotable via a mechanical drive. In DE 10 2011 005 312 A1 a cover is shown whose cover element is formed by a dimensionally stable tail fin of the stabilizer fin. For this purpose the stabilizer fin is correspondingly pivotable in the fin box, and the tail fin is correspondingly adjustable relative to the stabilizer fin. While the use of the tail fin as cover element requires no additional cover element or drive, an at least partial covering of the opening is, however, not possible with extended stabilizer fin.
In the publication DE 25 34 915 A1 a device for the stabilizing of ships is shown. For receiving the stabilizer fin in the rest position the device includes a fin-shaft housing including a slot as extension through which the stabilizer fin is extended and retracted. Here a plate for covering the fin-shaft housing is disposed on the stabilizer fin itself. In the use position of the stabilizer fin the plate covers the fin-shaft housing. In the rest position of the stabilizer fin a second plate can cover the fin-shaft housing. The slot remains uncovered independent of the position of the stabilizer fin.
Further prior art is known, for example, from GB 760 792 A and EP 2 096 027 A2.
An object of the invention is to provide a fin stabilizer that allows, with a reduced expense in terms of device technology, an at least partial covering of its fin-box opening both in the retracted and in the extended state of the stabilizer fin. Furthermore, it is an object of the invention to provide a cover element for such a fin stabilizer and a watercraft such that the watercraft has a high rolling damping and a lower fuel consumption.
An inventive fin stabilizer for stabilizing of watercraft has a pivotable stabilizer fin, a receiving space for receiving of the stabilizer fin in the retracted state, and at least one cover element for at least sectional covering of an opening of the receiving space, through which the stabilizer fin enters in the receiving space or exits during retracting and extending. According to the invention the at least one cover element is flexible.
Since the at least one cover element is flexible it can be pushed away from the stabilizer fin during extending or retracting, or reduced by the water pressure surrounding it for extending or retracting. Since the cover is not formed by a tail fin, it makes possible an at least partial closing of the opening even in the extended state of the stabilizer fin. Thus in operation a smoother hull is provided in the region of the stabilizer fin than with a completely open receiving space, i.e., a nearly continuous hull, whereby a more undisturbed flow is achieved. The buoyancy of the stabilizer fin is thus increased and a correspondingly high stabilizing performance is achieved. At the same time the flow resistance is significantly reduced by the nearly smooth hull in the region of the stabilizer fin, whereby the fuel consumption turns out significantly lower than with watercraft including open fin boxes in operation. Due to the greater buoyancy the efficiency of the fin stabilizer is increased with simultaneous resistance reduction.
In one exemplary embodiment the at least one cover element extends over the respective height of the opening or nearly over the respective height of the opening. Thus only one cover element is required. For example, the cover element is attached to an upper opening edge and protrudes in the closed position up to the lower opening edge.
Alternatively at least one second cover element can be provided that in combination with the at least one cover element extends over the respective height of the opening or nearly over the respective height of the opening. The second cover element is fastened, for example, on the lower opening edge and extends toward the upper opening edge. The at least one cover element is then fastened on the upper opening edge and extends toward the lower opening edge. The cover elements can have the same height and thus meet at virtually half the height of the opening or form a contact region at half the height of the opening. Of course the cover elements can also have different heights and, for example, the upper cover element can be taller than the lower cover element. The height of the cover elements preferably conforms to the position of the stabilizer fin in the put-away or retracted or extended state.
In one alternative exemplary embodiment including at least one second cover element, in the retracted state the cover elements abut on opposing sides of the stabilizer fin. In this exemplary embodiment the cover elements form no contact region between each other, rather each cover element forms its own contact region with one side of the stabilizer fin. In the retracted state the stabilizer fin is thus not completely covered by the cover elements, but rather protrudes out between them with a section, wherein the receiving space is closed by the opposing abutting or contact regions of the cover elements on the stabilizer fin. This exemplary embodiment allows a greater tolerance range with respect to the orientation and shape of the cover elements with respect to each other, since installation- and component-tolerances can be compensated by the respective abutting on the stabilizer fin in the retracted state. In addition, it can be advantageous in terms of a lower space requirement with, for example, retrofits.
In one exemplary embodiment the at least one cover element and/or the at least second cover element is/are an inherently stable and elastic plastic lip. In this purely passive variant any drive is eliminated. With extending of the stabilizer fin the at least one plastic lip is pushed away by it and correspondingly elastically deformed. Due to the lack of drive this variant is very low-maintenance. Natural rubber or a rubber material is preferably selected as material for the plastic lip. “Inherently stable” means that with lower attachment the plastic lip supports itself and does not bend away, thus requires no support framework. “Elastic” means ideally elastic and thus with a return into its original shape after an elastic deforming.
In one alternative exemplary embodiment the at least one cover element and/or the at least second cover element is/are an elastic plastic lip that is/are stabilized by at least one elastic or volume-variable support element. In this variant the plastic lips can be thinner and thus more easily embodied than the inherently stable and elastic plastic lips, since the stability is achieved by the local support elements. Tighter bends are thus possible than in the previous exemplary embodiment, with the result that this can be used in particular in the fin stabilizers that have a very narrow gap between the stabilizer fin and the upper and lower opening edge during retracting and extending. For example, for elastic support elements metallic spring plates or spring strips are attached rear-side on the at least one plastic lip or embedded therein. A further example are flexible support fibers made from carbon fibers or glass fibers that are embedded into the at least one plastic lip. One example for volume-variable support elements are hollow-chamber ribs that are depressurized during retracting and extending and are pressurized and thus stiffened for closing with a gaseous or liquid fluid or pressure medium such as compressed air, for example, via an already available onboard network. Due to a water pressure abutting on the hollow-chamber ribs their depressurization can be effected automatically with pressurization with compressed air. The compressed air thus need not be actively sucked away.
In a further exemplary embodiment the at least one cover element and/or the at least second cover element includes/include a plurality inherently stable and elastic bristle- or lamella-type elements. This variant is also purely passive. The bristle- or lamella-type elements can be lamella-type, bristle-type, barbel-type and the like.
In another exemplary embodiment the at least one cover element and/or the at least second cover element is/are a volume-variable hollow-chamber lip. The at least one hollow-chamber lip is pressurized with a fluid or pressure medium such as air, water, oil, and the like for at least partial covering of the opening, and depressurized for retraction and extension and thus pressed together. In particular when the hollow-chamber lip is pressurized with compressed air the depressurization can be effected automatically via the externally abutting water pressure, i.e., passively. In principle, however, an active sucking away of the air such as preferably with a liquid pressure medium is also possible. However, with the sucking away the externally abutting water pressure can be considered supporting. With this variant a strong elastic deforming does not occur with retracting and extending. However, the point in time of extending and retracting of the stabilizer fin can be set such that the stabilizer fin only retracts or extends a certain pressed-out or discharged fluid amount from the at least one hollow-chamber lip. Possible leaks in the hull of the hollow-chamber lip can be immediately recognized via pressure fluctuations during the pressurizing in the at least partially closed state. Expensive inspection work, which can only be carried out in dry dock, is thus omitted.
In order to achieve an optimal at least partial covering of the opening, the at least one hollow-chamber lip includes at least one flexible and high-tensile-strength shaping element. A high dimensional- and thus fit-precision of the at least one seal lip is achieved by the tensile strength. The flexibility makes it possible that the at least one hollow-chamber lip is nonetheless compressible or foldable. Examples of such a shaping element are fabric sheets that extend in the interior of the at least one hollow-chamber lip and make possible via holes a pressure equalization between the chambers formed by them.
To protect the at least one hollow-chamber lip from damage by the stabilizer fin a robust and simultaneously elastic or flexible belt element, such as, for example, a conveyor band, can be disposed between the stabilizer fin and the hollow-chamber lip. The at least one hollow-chamber lip is thus protected from direct physical contact with the stabilizer fin. Simultaneously the at least one belt element can serve as a guide for the at least one hollow-chamber lip. In order to ensure a reliable guiding of the hollow-chamber lip out of the fin-box opening with a steep installation position of the respective fin box, the respective belt element can be stiffened by a reinforcement.
In one preferred exemplary embodiment the at least one first cover element includes at least one buoyancy body for generating a buoyancy. The folding, retracting, or extending of the upper hollow-chamber lip from the fin-box opening can thereby be accelerated independent of the installation position of the fin box.
According to one further exemplary embodiment of the device the at least second cover element is weighted by at least one downward force providing elementfor generating a downward force. A folding together or pivoting-out of the hollow-chamber lip is accelerated by the downward force providing element during opening of the fin box. It can thereby also be ensured that the cover element reliably escapes from the opening region and thus from the pivot path of the stabilizer fin.
In one further exemplary embodiment of the device the fin box includes in the upper edge region an upper receiving space for receiving an upper cover element and/or, in the lower edge region, a lower receiving space for receiving a lower cover element. In the opened state of the fin box the receiving elements are thereby securely protected from external damage.
An inventive cover element for a fin stabilizer is flexible. It is thus not rigid, stiff, but rather elastic, in particular ideally deformable, flexible, volume-variable, and the like. Due to the flexibility, device-technical expensive articulation or movement mechanisms for opening or closing the cover element during extending and retracting of a stabilizer fin are omitted.
An inventive watercraft is a ship and has at least one inventive fin stabilizer. Such a ship has a high roll damping and a lower fuel consumption than ships with open fin boxes in operation.
In the following, preferred exemplary embodiments of the invention are explained in more detail with reference to greatly simplified schematic illustrations.